1. Field of the Invention
The present invention relates to an extension bar and, particularly, to an extension bar that is able to engage a driving member with a pneumatic tool securely, and also adapted to allow the driving member to be released therefrom in an easy manner.
2. Description of the Related Art
U.S. Pat. No. 8,070,377 shows a quick-release coupler including a rod having first and second sections. The first section includes an end for coupling with a pneumatic tool. The second section extends from the other end of the first section. A sleeve is slidably mounted around the rod and includes an end for releasably coupling a bit. The sleeve includes an axial bore having larger and smaller sections. The larger section has polygonal cross sections corresponding to polygonal cross sections of the first section. A radial bore is formed in the sleeve and in communication with the smaller section. A ball is moveably received in the radial bore and moveably received in a recess of the second section of the rod to releasably engage the sleeve with the bit. A spring is mounted in the larger section of the sleeve for biasing the sleeve towards the other end of the rod.
When the quick-release coupler is driven by a pneumatic tool, there exists a vibration, and such vibration can cause the sleeve to slide relative to the rod to a position which a bit held in the quick-release coupler is inadvertently released. Additionally, when spring fatigue happens, the quick-release coupler is no longer able to hold the bit securely.
The present invention is, therefore, intended to obviate or at least alleviate the problems encountered in the prior art.